Image forming apparatuses that include a plurality of paper feed sources and form an image on a sheet fed from a selected paper feed source are widely known. A user who performs printing using such image forming apparatuses issues a print instruction by designating a paper feed source from which a loaded sheet is to be fed for printing via a printer driver. Japanese Patent Laid-Open No. 2013-256097 suggests a setting that causes an image forming apparatus to automatically select a paper feed source loaded with sheets that satisfy print conditions designated by a user via a printer driver.
Sheets to be used in image forming apparatuses for printing come in a wide variety of types, from thick paper to thin paper. Therefore, image forming conditions, such as a fixing temperature and a conveyance speed, are changed in accordance with a paper type in the image forming apparatuses to suppress, for example, detachment of fixed toner and curling of sheets.
Conventionally, the types of sheets loaded in paper feed sources of image forming apparatuses are manually set by a user. In some image forming apparatuses of today, paper feed sources are provided with sensing devices called media sensors, and the types of sheets loaded in the paper feed sources are automatically detected by observing the optical characteristics of the surfaces of such sheets. Japanese Patent Laid-Open No. 2013-236178 and Japanese Patent Laid-Open No. 2010-282204 disclose a technique to cause an image forming apparatus to discharge a blank sheet without performing printing when the paper type detected by a media sensor does not match the paper type designated by a user via a printer driver.
Providing each paper feed source with a media sensor in the above-described manner leads to a cost increase. In view of this, a media sensor used in common can be provided on a conveyance path for sheets. With this structure, the type of a sheet conveyed from each paper feed source can be detected when the sheet is at the position of the sensor. In this case, if it is determined that the type of a sheet detected by the media sensor is inappropriate because it does not match the paper type set by a user for printing, the presence of the sheet on the conveyance path prohibits feeding of a sheet from another paper feed source.
With conventional technology, when the detected paper type does not match the paper type set by a user, a blank sheet is discharged without performing printing. However, the presence of a blank sheet in printed products means the presence of an unintended sheet, this could be undesirable for the user. Furthermore, when a paper feed source to be used in printing is automatically selected, the type of sheets loaded in each paper feed source is unknown at the start of a job. Therefore, it may be necessary to convey a sheet loaded in each paper feed source to the position of a media sensor to detect its paper type. If the detection result does not match the paper type included in the print settings configured by the user, the sheet is discharged as-is, that is to say, as a blank sheet. Such a presence of a blank sheet in printed products means the presence of an unintended sheet, this could be undesirable for the user.